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Ninja flex jamming in Hemera

Upgraded Ender 3 with Hemera and it works great for PLA, PETG and even TPU. But when Ninja flex filament is used the filament extrudes a little and then the gears slip and nothing comes out of the nozzle. If I now remove the Ninjaflex filament and try PLA then it works fine. Trying Ninja flex again will result in the same type of jam.

I have tried various temperatures from 200 to all the way to 250. Here is the Ninja flex filament

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3 Answers

What retraction settings are you using? Softer filaments will tend to separate in the hotend if retracted too heavily, and my experience so far with the Hemera is that it requires very little retraction. Try running a retraction test going from no retraction at all and moving up? I’m currently running PLA at 0.25mm retraction, 20mm/sec with nearly stringing-free prints.

Also, flexibles seem to, in general, require the extruder to exert a bit less force on them or else the gears will grind/compress them, so I’d recommend reducing the tension a bit on the adjustment screw.

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Current settings are 0.8mm for retractions. But the jamming occurs even when I try to just extrude with the nozzle lifted high.

Not sure if I should call it jamming, as if I retract the filament will come back out, and part of the filament looks chewed up in the gears.

I will try to reduce the tension to see if that helps. Thanks


Worth giving a try - Bondtech for example recommend much lowered tension (minus 3-4 turns instead of minus 1.5-2) for TPU and other flexibles when using a BMG, which is "similar" in the way that it's another dual gear extruder. Guess could explain the chewed up look...


Tried another print after a PLA print was done, reduced the tension and saw good extrusion at first.

The first layer was better, but overall was still under extruding. And with higher speed at second layer the under extrusion was too much to overcome.

Tried an extrusion test used to calibrate Esteps and overall it was under extruding by 50% (only extruded 50mm for 100mm)

So not sure if there is other filament stuck in there, or my build has issues.

Switched over to PLA and no under extrusion.

Will contact support


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Hi Ravindra,

Our advice with Hemera is to increase the tension when printing with flexible materials. If you continue to have issues with jamming please contact

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Hi all,

After installing my hemera on my anycubic chiron I experienced the same issues printing flexible filament. I seem to have fixed it with a number of small tweaks:

  1. Ensure the heat paste is applied to the section above the thread as well on the heat break as I discovered filament was softening in the upper heat break and causing friction. Make sure you clean any excess off after reassembly.
  2. Polish the filament entry into the heat break, mine had a rough finish with a blunt burr which was grabbing the filament if expanded due to compression of the feed.
  3. Reduce the drive tension to ~10% to prevent flattening of the filament which binds on the entry of the heat break.
  4. Feed the filament from above the printer with as little resistance as possible, without the small pfte tube.

After doing this I could print 85a tpu without issue inline with what you see on YouTube.

I hope this helps.

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Ravindra will be eternally grateful.
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